Screening of bacteria for the suppression of Botrytis cinerea and Rhizoctonia solani on lettuce (Lactuca sativa) using leaf disc bioassays |
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Authors: | P J FIDDAMAN T M O'NEILL S ROSSALL |
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Affiliation: | Division of Plant Science, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Sutton Bonington, Loughborough, Leics, LE12 5RD, UK;ADAS Arthur Rickwood, Mepal, Ely, Cambs CB6 2BA, UK |
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Abstract: | Two leaf disc bioassays were developed for screening bacteria as putative biological control agents of Botrytis cinerea and Rhizoctonia solani on lettuce. Aerobic spore and non‐spore forming bacteria were isolated from the phylloplane, rhizoplane and rhizosphere of symptom‐free lettuce plants grown in the presence and absence of chitin or composted bark soil amendments. Bacteria, previously isolated from other plants, were also included in the primary screen initially against B. cinerea. One hundred and twenty‐seven of 700 isolates reduced botrytis rotting of lettuce leaves by more than 50% in the primary screen. Following a secondary screen against B. cinerea, the lead 50 isolates were also tested for suppression of R. solani infection. Four isolates significantly reduced both botrytis and rhizoctonia leaf rotting. Eleven and five isolates gave control of botrytis and rhizoctonia, respectively, equal to that given by the standard fungicides Rovral WP (iprodione) and Basilex (tolclofos methyl). The two most effective isolates against B. cinerea and R. solani were both identified as Bacillus subtilis. Use of soil amendments did not increase the proportion of efficacious isolates recovered. Effective isolates were originally recovered from roots of oilseed rape and lettuce leaves. In general, it was found that bacteria which controlled one disease effectively did not control the second disease nearly as well. The bioassay protocols developed in this study were used successfully in screening a large number of bacterial isolates in a short time. |
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Keywords: | Botrytis Rhizoctonia Bacillus glasshouse crops biocontrol fungicide reduction |
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